A sixth person has been confirmed dead in the explosion that flattened two apartment buildings in Harlem. A fire department spokesman says the unidentified body was pulled out of the rubble around 3:15 a.m.

Update at 3:55 a.m. ET, March 13:

The explosion that destroyed two apartment buildings in Harlem on Wednesday has claimed the life of a fifth person. The body of an adult female was found around 2:50 a.m. Thursday, according to The Associated Press. At least five people are unaccounted for.

Update at 2 a.m. ET, March 13:

A fourth person has been confirmed dead in Wednesday's explosion, according to fire department spokesman Jim Long. He says the unidentified adult male was pulled from the rubble shortly after midnight. Nine people are missing and more than 60 are injured.

New York Mayor Bill de Blasio's office said Wednesday evening that the death toll had gone up to three, from the two dead reported earlier. The mayor's office said nine were missing.

The explosion occurred at 1646 Park Ave.

De Blasio, speaking at news conference earlier in the day, described the incident, which occurred at about 9:30 a.m. ET, as "a tragedy of the worst kind."

He said that there were people still missing from the blast that affected buildings in an around the center of the explosion. He said the response to the explosion would "be an extended operation."

Fire Commissioner Salvatore Cassano said the building where the explosion was thought to have occurred "appears not to be there anymore."

Con Ed tweets that its workers were responding to a report of a gas odor at 1652 Park. The utility says the call came in at 9:13 a.m. and that crews were dispatched a few minutes later and arrived on the scene after the explosion.

De Blasio said preliminary reports are that there was no indication of a problem before that call.

It's the first major emergency since de Blasio took office.

Officials say there was no major damage to other buildings in the area, but Beverly MacFarlane, who lives a block away, tells NPR's Joel Rose that when she rushed back from work after hearing about the explosion, she found "my pictures ... on my wall [were] on the floor."